Repair error noticed by Roberto Cornacchia: selectivity code

was rejecting negative attnums as bogus, which of course they are not.
Add code to get_attdisbursion to produce a useful value for OID attribute,
since VACUUM does not store stats for system attributes.
Also, repair bug that's been in eqjoinsel for a long time: it was taking
the max of the two columns' disbursions, whereas it should use the min.

src/backend/optimizer/path/clausesel.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.25 1999/07/25 23:07:24 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.26 1999/09/09 02:35:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -230,17 +230,7 @@ compute_clause_selec(Query *root, Node *clause)
 				int			flag;
 
 				get_relattval(clause, 0, &relidx, &attno, &constval, &flag);
-				if (relidx <= 0 || attno <= 0)
-				{
-					/*
-					 * attno can be Invalid if the clause had a function in it,
-					 * i.e.   WHERE myFunc(f) = 10
-					 *
-					 * XXX should be FIXED to use function selectivity
-					 */
-					s1 = (Cost) (0.5);
-				}
-				else
+				if (relidx && attno)
 					s1 = (Cost) restriction_selectivity(oprrest,
 														opno,
 														getrelid(relidx,
@@ -248,6 +238,16 @@ compute_clause_selec(Query *root, Node *clause)
 														attno,
 														constval,
 														flag);
+				else
+				{
+					/*
+					 * attno can be 0 if the clause had a function in it,
+					 * i.e.   WHERE myFunc(f) = 10
+					 *
+					 * XXX should be FIXED to use function selectivity
+					 */
+					s1 = (Cost) (0.5);
+				}
 			}
 		}
 		else
@@ -274,7 +274,8 @@ compute_clause_selec(Query *root, Node *clause)
 							attno2;
 
 				get_rels_atts(clause, &relid1, &attno1, &relid2, &attno2);
-				if (relid1 > 0 && relid2 > 0 && attno1 > 0 && attno2 > 0)
+				if (relid1 && relid2 && attno1 && attno2)
+
 					s1 = (Cost) join_selectivity(oprjoin,
 												 opno,
 												 getrelid(relid1,

src/backend/optimizer/util/clauses.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.50 1999/08/26 05:09:05 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.51 1999/09/09 02:35:53 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -116,7 +116,10 @@ make_opclause(Oper *op, Var *leftop, Var *rightop)
  *
  * Returns the left operand of a clause of the form (op expr expr)
  *		or (op expr)
- * NB: it is assumed (for now) that all expr must be Var nodes
+ *
+ * NB: for historical reasons, the result is declared Var *, even
+ * though many callers can cope with results that are not Vars.
+ * The result really ought to be declared Expr * or Node *.
  */
 Var *
 get_leftop(Expr *clause)
@@ -549,8 +552,11 @@ NumRelids(Node *clause)
  *			if the "something" is a constant, the value of the constant
  *			flags indicating whether a constant was found, and on which side.
  *		Default values are returned if the expression is too complicated,
- *		specifically -1 for the relid and attno, 0 for the constant value.
- *		Note that InvalidAttrNumber is *not* -1, but 0.
+ *		specifically 0 for the relid and attno, 0 for the constant value.
+ *
+ *		Note that negative attno values are *not* invalid, but represent
+ *		system attributes such as OID.  It's sufficient to check for relid=0
+ *		to determine whether the routine succeeded.
  */
 void
 get_relattval(Node *clause,
@@ -610,8 +616,8 @@ get_relattval(Node *clause,
 	{
 		/* Duh, it's too complicated for me... */
 default_results:
-		*relid = -1;
-		*attno = -1;
+		*relid = 0;
+		*attno = 0;
 		*constval = 0;
 		*flag = 0;
 		return;
@@ -663,7 +669,7 @@ static int is_single_func(Node *node)
  *		for a joinclause.
  *
  * If the clause is not of the form (var op var) or if any of the vars
- * refer to nested attributes, then -1's are returned.
+ * refer to nested attributes, then zeroes are returned.
  *
  */
 void
@@ -674,10 +680,10 @@ get_rels_atts(Node *clause,
 			  AttrNumber *attno2)
 {
 	/* set default values */
-	*relid1 = -1;
-	*attno1 = -1;
-	*relid2 = -1;
-	*attno2 = -1;
+	*relid1 = 0;
+	*attno1 = 0;
+	*relid2 = 0;
+	*attno2 = 0;
 
 	if (is_opclause(clause))
 	{

src/backend/optimizer/util/plancat.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.36 1999/07/25 23:07:26 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.37 1999/09/09 02:35:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -288,7 +288,7 @@ index_selectivity(Query *root,
 }
 
 /*
- * restriction_selectivity in lisp system.
+ * restriction_selectivity
  *
  *	  NOTE: The routine is now merged with RestrictionClauseSelectivity
  *	  as defined in plancat.c
@@ -298,7 +298,7 @@ index_selectivity(Query *root,
  * operator relation, by calling the function manager.
  *
  * XXX The assumption in the selectivity procedures is that if the
- *		relation OIDs or attribute numbers are -1, then the clause
+ *		relation OIDs or attribute numbers are 0, then the clause
  *		isn't of the form (op var const).
  */
 Cost
@@ -337,7 +337,7 @@ restriction_selectivity(Oid functionObjectId,
  *	  information.
  *
  * XXX The assumption in the selectivity procedures is that if the
- *		relation OIDs or attribute numbers are -1, then the clause
+ *		relation OIDs or attribute numbers are 0, then the clause
  *		isn't of the form (op var var).
  */
 Cost